Difficulty accurately identifying internal versus external hires and counts

Summary

Several data elements are combined to indicate if a hire is internal versus external to ensure accuracy in the data. Our formula works but doesn't seem efficient and we can't easily get to a count.

Content

I'd appreciate any help from the community.  This is my first post and this one is kindof a doozy.

My end goal: Present a chart that mirrors the Recruiting - External Position Trends chart in the Sample Recruiting Dashboard.  Where we've gotten stuck is creating counts. The issue seems to be the complexity of how we identify an internal candidates. 

Context:  We are a large retailer and it is extremely difficult with turnover to ensure that all candidates are coming through our internal portal to apply to new roles. Therefore, a candidate is considered internal as follows: if candidate type for UDF is internal (selected by recruiters on the offer grid), if the submissions is internal,